COMPARATIVE  PHYSIOLOGICAL  STUDIES  OF 
STRAINS  OF  CORN  RESISTANT  AND 
SUSCEPTIBLE  TO  DISEASE 


BY 

FREDERICK  FRANCIS  WEINARD 

B.S.  University  of  Nebraska,  1916 
M.A.  University  of  Nebraska,  1917 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 
FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY  IN  BOTANY 
IN  THE  GRADUATE  SCHOOL  OF  THE  UNIVERSITY 
OF  ILLINOIS,  1922 


URBANA,  ILLINOIS 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/comparativephysiOOwein 


Table  of  Contents 


Page 

I.  Introduction  1 

II.  Materials  and  methods  2 

III.  Experimental  work  3 

Absorption  of  water  at  different 

temperatures  3 

The  effect  of  temperature  on 

germination  and  growth  17 

Vitality  as  influenced  by  soaking 

in  water  22 

Vitality  as  influenced  by  growth 

of  fungi  29 

IV.  Discussion 32 

V.  Conclusions  34 

VI.  Acknowledgment  35 

VII.  Literature  cited  36 

VIII.  Plates  38 

IX.  Vita  51 


-1 


Comparative  Physiological  Studies  of  Strains  of  Corn 
Resistant  and  Susceptible  to  Disease 

I.  Introduction 

Since  the  work  of  Burrill  and  Barrett  (5,6),  corn 
root  and  stalk  rots  have  come  to  be  generally  recognized  as 
factors  limiting  the  crop.  In  recent  years  especially,  demon- 
stration of  the  widespread  occurrence  of  these  diseases  through- 
out corn  growing  regions  has  served  to  augment  their  importance 
and  to  turn  the  light  of  many  investigations  upon  them. 

Reduction  in  yield  in  the  field  has  been  repeatedly 
correlated  with  the  presence  of  fungi,  commonly  species  of 
Fusarium  or  of  Diplodia,  in  the  seed.  As  a result,  germinator 
tests  designed  to  eliminate  such  infested  seed  have  been  widely 
and  more  or  less  successfully  used. 

It  has  been  observed  by  Holbert  (9),  that  corn  with 
a good  record  on  the  germinator  will  not  always  show  the  same 
comparative  performance  in  the  field.  Marked  differences  may 
be  obtained  in  the  yields  of  apparently  disease-free  ears  when 
planted  in  infested  soil.  There  are  apparently,  resistant  and 
susceptible  strains  within  the  variety. 

A physiological  comparison  of  three  such  strains,  one 


' 

. 


. 


. 


' 

I Jtw  C*  I-.'  t r tu  ; I ’ • "|  C 6i'  t tr  1 


. 


♦ 


-2- 

resistant,  and  two  of  different  degrees  of  susceptibility,  has 
been  undertaken  in  the  present  investigation.  The  work  was 
done  in  the  Plant  Physiology  Laboratories  of  the  University  of 
Illinois. 

II.  Materials  and  Methods 

Reid’s  Yellow  Dent  corn,  supplied  by  Mr.  J.  R. 
Holbert,  Bloomington,  Illinois,  was  used  in  the  tests.  About 
50  ears  each  of  "Peoria  Co.  Good" (PCG),  "Peoria  Co.  Bad"(PCB), 
and  "Fox" (Fox)  were  available  from  which  to  obtain  representa- 
tive samples.  Typical  ears  of  each  kind  are  illustrated  in 
Plates  1 to  4.  Data  on  the  viability,  amount  of  fungous  in- 
festation, physical  composition,  and  kernel  indentation  in  the 
three  types  are  given  in  Tables  1 to  3 (unpublished  notes  - 
J.  R.  Holbert). 


Table  1.  Viability  and  per  cent  of  infestation. 
Vitality  Fusarium  Diplodia 


(PCG) 

99.40 

.90 

0 

(PCB) 

99.48 

3.45 

0 

(Fox) 

96.50 

13.70 

1.5 

Table  3. 

Physical 

Horny 

composition. 

Medium  Starchy 

(PCG) 

70.4 

28.4 

1.3 

(PCB) 

15.5 

59.3 

25.3 

(Fox) 

7.3 

79.4 

13.4 

-3- 


Table  3.  Indentation  of  kernels. 


Smooth  Medium  Rough 


pea) 

PCB) 

Fox) 


63.5  36.4  1.1 

14.3  33.6  53.1 

3.1  34.7  73.3 


In  general,  the  kernels  of  (PCG),  the  "resistant” 


strain,  are  characteristically  plump,  hard,  smoothly  dented, 
rich  orange  in  color,  and  with  a bright  lustre.  The  kernels 
of  (PCB),  and  of  (Fox)  corn,  respectively  "susceptible"  and 
"very  susceptible",  are  often  somewhat  shriveled,  starchy, 
usually  roughened  at  the  crown,  pale  in  color,  lacking  in  lustre* 
As  the  methods  used  in  this  investigation  varied 
with  each  phase  of  the  problem,  they  will  be  referred  to  in 
the  order  of  experiment. 


Absorption  of  water  at  different  temperatures. 

Water  absorption,  one  of  the  earliest  and  most  im- 
portant processes  in  the  germinating  seed,  offers  the  first 
logical  point  of  comparison.  50  kernels,  5 from  each  of  ten 
typical  ears,  were  used  in  each  experiment.  Effort  was  made 
to  select  only  kernels  with  coats  intact. 

The  kernels  were  placed  in  perforated  aluminum  con- 


III.  Experimental  Work 


■ 


. 


. 


- 

. 


. 


- 


-4- 


tainers  and  immersed  in  jars  containing  600  cc.  of  distilled 
water  at  t emperat ures  of  10w  C. , 15°  C.  , 20°  C.,  and  35°  C. , 
respectively.  These  temperatures  were  maintained  by  means  of 
the  large  constant  temperature  cases  in  the  Plant  Physiology 
Laboratories.  At  half  hour  intervals,  the  seeds  were  removed, 
superficially  dried,  and  weighed  on  a balance  in  closed  glass 
dishes.  Data  for  the  first  9 hours  were  obtained  from  one 
set  of  kernels,  and  for  a second  9 hours  before  weighing 
commenced.  The  comparative  rates  of  absorption  at  the  differ- 
ent temperatures  are  shown  in  Figures  1 to  8. 

The  velocities  of  absorption  at  points  of  equal  in- 
take are  shown  in  Tables  4 to  7.  The  velocity  at  any  given 
point  is  represented  approximately  by  the  tangent  of  the  angle 
formed  by  the  straight  line  between  two  points  determined  ex- 
perimentally, with  the  time  axis.  This  straight  line  is  a 
chord  parallel  to  the  tangent  at  some  intermediate  point  on  a 
smooth  curve  joining  the  two  known  points.  Brown  and  Worley 
(4)  measured  the  tangents  by  means  of  string  and  protractor. 
Their  "ideal  curves”  were  constructed  from  relatively  few 
known  points.  Shull  (16)  calculated  the  tangents  from  alge- 
braic formulae  of  the  curves.  In  view  of  the  comparatively 
large  number  of  known  points,  it  is  thought  that  fair  accuracy 
is  attainable  by  the  method  employed  in  the  present  work. 


. 

. 

* ’l 


■ 


. 


. 


' ' 


. 


Fig.  4.  Water  absorption  at  15 
deg.  C. 


(PCS) 


vjn 

o 


ro 


M 

oi  _2 

.1- 

ro 

o 


t 

ro 

nji 

V>J 

O 


VM 


VJ1 


ON 


H* 

09 


Oft 


<o 


o 

Q 


-13- 


Table  4. 

Comparati 

vs  velocities  at  10 

Per  cent 
intake 

(PCG) 

(PCB) 

(Fox) 

3.5 

2.05030 

2.60510 

3.29980 

5.0 

3.05030 

3. 60510 

2. 29980 

7.5 

. 34433 

.93352 

.46631 

10.0 

.38386 

.46631 

.50953 

13.5 

.44523 

.54396 

.38386 

15.0 

. 34433 

. 39391 

.28675 

17.5 

.40403 

.40403 

. 36795 

20.0 

.36795 

.15838 

. 33087 

Mean 

. 78629 

1.01354 

.84311 

Ratios 

1.00  : 

1.39  : 

1.-07 

Table  5. 

Comparative 

velocities  at  15 

Per  cent 
intake 

(PCG) 

(PCB) 

(Fox) 

2.5 

2.34600 

2.90430 

2.24600 

5.0 

2.24600 

2.90430 

3.24600 

7.5 

.61280 

.83910 

.75355 

10.0 

.49858 

.66139 

. 50953 

12.5 

.31530 

.57735 

.42447 

15.0 

. 36397 

.44523 

.48773 

17.5 

. 61280 

.53171 

.48773 

20.0 

. 31530 

.41421 

.39631 

Mean 

.90134 

1.15974 

.93140 

Hatios 

1.00  : 

1.29  : 

1.03 

Table  6. 

Comparative 

s velocities  at  30 

Per  cent 
intake 

(PCG) 

(PCB) 

(Fox) 

3.5 

2.47510 

3.07770 

2.67460 

5.0 

2.47510 

3.07770 

2.67460 

7.5 

.83910 

3.07770 

.80978 

10.0 

.78129 

1.00000 

.63487 

12.5 

.39391 

.62487 

.46631 

15.0 

.61280 

.61280 

.55431 

17.5 

. 31356 

. 67451 

.53171 

20.0 

.30573 

. 36397 

. 70031 

Mean 

1.01195 

1.56366 

1.12955 

Ratios 

1.00 

1.54 

1.12 

-14- 


Table  7. 

Comparative  velocities  at  35°  C. 

Per  cent 
intake 

(PCG) 

(PCB) 

(Fox) 

3.5 

3.07770 

3.86670 

3. 73310 

5.0 

3.07770 

3.86670 

3.73310 

7.5 

3.07770 

3.86670 

3.73310 

10.0 

1. 51080 

1.80400 

1.33490 

13.5 

.98370 

1 . 80400 

1.33490 

15.0 

1.05380 

1.00000 

1.33490 

17.  5 

1.03550 

1.00000 

1.19180 

30.0 

.78139 

. 83434 

. 86939 

Mean 

1.83465 

3.35405 

3.13036 

Ratios 

1.00  : 

1.34 

: 1.16 

For  comparison,  the 

relative 

rates  of  absorption  at 

kernels 

with  coats 

broken,  is 

shown  in  Figure  7 

(upper  curves).  The  corresponding  velocities  at  points  of 
equal  intake  are  given  in  Table  8. 


Table  8.  Comparative  velocities  at  35°  C. (coats 
broken) . 


Per  cent 
intake 

(PCG) 

(PCB) 

(Fox) 

3.5 

3.7331 

4.3315 

3.8667 

5.0 

3.7331 

4.3315 

3.3667 

7.  5 

3.7331 

4. 3315 

3.8667 

10.0 

3.7331 

4.3315 

3.8667 

13.  5 

1.3799 

1.7331 

1.4550 

15.0 

1.3764 

1.7331 

1.7675 

17.5 

1 . 0734 

1.5108 

1.7675 

30.0 

1.0734 

1.5108 

1.7675 

Mean 

3.4663 

3.9765 

3.6738 

Ratios 

1.00  : 

1.31  : 

1.08 

-15- 


(PCB)  and  (Fox)  corn  show  a constant  higher  rate 
of  water  absorption  than  Peoria  Co.  Good.  If  the  rate  in 
the  latter  case  be  taken  as  1.00,  then  the  others  stand  to 
it  in  the  mean  ratios  of  1.31  and  1.09  respectively.  There 
is  but  little  variation  from  these  ratios  as  the  temperature 
changes. 

Kernels  with  broken  coats  exhibit,  as  might  be  ex- 
pected, a uniformily  higher  rate  of  absorption  than  kernels 
with  coats  intact.  But  the  relative  rates  for  the  three 
samples  of  corn  remain  essentially  the  same,  regardless  of 
whether  the  absorption  is  by  kernels  with  coats  intact  or 
kernels  with  broken  coats  (Fig.  7,  Tables  7 & 8).  Hence  the 
differences  observed  between  the  three  types  of  kernels  may 
not  be  ascribed  to  modifications  in  the  coats  but  rather  to 
differences  in  the  nature  of  the  stored  materials  in  the  ker- 
nels. The  marked  correlation  between  the  percentages  of  soft 
starchy  kernels  and  absorption  rates  would  tend  to  establish 
the  latter  hypothesis. 

In  order  to  determine  the  specific  effect  of  temperat- 
ure on  the  rate  of  absorption  in  corn,  the  temperature  coeffi- 
cient, Q , was  commuted  from  the  data  in  Tables  4 to  7.  The 
10 

value  of  Q has  been  calculated  for  different  combinations  of 

10 

temperature?,  using  the  formula  of  Kanitz  (11).  The  results 


are  given  in  Table  9. 


-16- 


Table  9.  Q1q  for  different  comb inati one  of 

temperatures . 


Temperatures 

(PCG) 

(PCB) 

(Fox) 

10°  C. -1 5°  C. 

1.31 

1. 31 

1.28 

10°  C . -20°  C. 

1.29 

1. 54 

1.34 

10°  C. -35°  C. 

1.40 

1.38 

1.45 

15°  C . -20°  C. 

1.26 

1.82 

1.47 

15°  C . -35°  C. 

1.42 

1. 30 

1.51 

20°  C . -35°  C. 

1.48 

1.27 

1.29 

Mean 

1.36 

1.44 

1.38 

The  mean  value  of  the  temperature  coefficient  of 
water  absorption  is  approximately  1.4  in  all  three  types  of 
corn.  Variations  in  the  value  obtained  may  occur  according 
to  the  temperatures  selected.  This  has  been  previously  pointed 
out  by  Denny  (7).  Shull  (15),  working  with  corn,  has  reported 
data  indicating  that  the  temperature  coefficient  is  about  1.5. 
Shull  (16)  obtained  in  previous  experiments  with  Xanthium  seeds 
values  of  1.55  and  1.83,  and  with  split  peas,  1.6.  Brown  and 
Worley  (4),  working  with  barley  seeds,  obtained  the  relatively 
high  values  of  1.8  and  2.02,  which  approximate  the  value  of 
the  coefficient  of  chemical  change.  The  results  of  the  present 
work  agree  with  those  of  Shull  (15,16),  showing  that  the  coeffi- 
cient of  water  absorption  by  seeds  of  corn  is  considerably  less 


than  2. 


. 


' 

. 

. 


. 


. 


. 


’ 


-17- 

The  effect  of  temperature 
on  germination  and  growth 

The  rate  of  germination  of  the  three  lots  of  corn 
was  tested  at  temperatures  of  10°  C. , 15°  C. , 20°  C. , 25°  C.  , 
and  30°  C.  5 seeds  of  each  kind  were  planted  in  Mason  jars 
at  a uniform  depth  of  3/4  inch  in  2i  inches  of  clean  flint 
sand,  with  moisture  contents  of  20%,  40%,  and  60%  of  saturation, 
respectively.  Repetition  yielding  essentially  similar  results, 
the  mean  figures  are  given  in  Tables  10  to  14.  The  time  from 
planting  to  appearance  of  the  shoot  at  the  surface  of  the  sand, 
and  per  cent  of  germination  are  shown  in  each  case. 

Table  10.  Rate  and  per  cent  of  germination  at  30°  C. 


Soil 

moisture 

20% 

40% 

6°$ 

Days 

1° 

Days 

1° 

Days  % 

(PCGr) 

2.6 

100 

2.4 

100 

2.0  100 

(PCB) 

2.7 

100 

2.6 

100 

2.4  100 

(Fox) 

2.8 

80 

2.5 

100 

2.4  100 

Table  : 

LI.  Rate  and 

per 

cent  of  germination  at  25°  C. 

Soil 

moisture 

20% 

40% 

eo $ _ 

Days 

t 

Days 

% 

Days  % 

(*CG) 

3.20 

100 

3.0 

100 

3.0  100 

(PCB) 

3.4 

90 

3.1 

100 

3.3  100 

(Fox) 

3.7 

100 

3.2 

100 

3.2  90 

-18- 


Table 


(POO) 

(pcb) 

(Fox) 


Table 


(PCG) 

(PCB) 

(Pox) 


13.  Rate  and  per  cent  of  germination  at  20°  C. 

. Soil  moisture 
30 $ 40 $ 60$ 


Days 

$ 

/ 

Days 

$ 

Days 

$ 

7.4 

100 

7.3 

100 

7.3 

100 

7.6 

100 

7.4 

100 

8.4 

90 

7.7 

90 

7.6 

90 

8.5 

80 

13. 

Rate 

and  per 

cent 

of  germination  at  15°  C. 

Soil  moisture 


30$ 

Days 

$ 

40$ 

Days 

$ 

60$ 

Days 

1o 

8.0 

100 

7.7 

100 

7.4 

100 

8.6 

100 

8.  7 

80 

8.  3 

100 

9.5 

100 

9.6 

100 

8.3 

70 

Table  14. 


Rate  and  per  cent  of  germination  at  10°  C. 


(PCG) 

m 


Soil  moisture 
30$  40$  60$ 

Days  $ Days  $ Days  $ 


38.3 

70 

28.0 

30 

35.5 

20 

30.4 

50 

32.7 

40 

33.0 

10 

0 

0 

34.0 

20 

37.  5 

20 

It  will  be  observed  that  the  differences  attributable 
to  soil  moisture  are  not  great.  Disregarding  this  factor,  the 
average  number  of  days  required  for  germination  at  each  temper- 
ature, and  the  ratios  representing  the  relative  performance  of 
each  lot  of  corn,  are  given  in  Table  15. 


-19- 


Table  15 

. Average  periods 

for  germinati 

at  the 

different  temperatures 

Temper- 

ature 

(PCG) 

(PCB) 

(Fox) 

30°  C. 

Days 

2.3 

2.5 

2.5 

Ratios 

1.00 

1.00^ 

: 1.09 

25°  C. 

Days 

3.1 

3.  3 

3.4 

Ratios 

1.00 

1.06 

: 1.10 

20°  C. 

Day  8 

7.3 

7.8 

7.9 

Ratios 

1.00 

1.07 

: 1.08 

15°  C. 

Days 

7.7 

8.5 

9.1 

Ratios 

1.00 

1.10 

: 1.18 

10°  C. 

Days 

30.5 

32.0 

35.  7 

Ratios 

1.00 

1.05 

: 1.17 

Mean  ratios 

1.00 

1.07 

: 1.12 

When  the  seedlings  at  the  different  temperatures  had 
grown  to  approximately  the  height  of  the  jars,  the  latter  were 
opened  and  the  roots  and  shoots  measured  with  a centimeter  rule 
Since  duplicate  experiments  gave  similar  results,  the  averages 
are  given  in  Tables  16  to  20. 


Table  16.  Comparative  growth  at  30°  C. 


Roots 


Shoots 


20 % 

40% 

60% 

Av. 

20% 

40% 

60% 

Av. 

(PCG) 

12.5 

15.4 

10.6 

12.8 

9.8 

14.6 

14.4 

12.9 

(PCB) 

13.3 

11.7 

13.5 

12,8 

9.9 

9.9 

14.9 

11.6 

(Fox) 

15.1 

10.3 

11.9 

12.4 

10.5 

9.8 

14.3 

11.7 

Table  17 

. Comparative  growth  at  25w 

C. 

Roots 

Shoots 

30% 

40% 

60% 

Av. 

20% 

40% 

60% 

Av. 

(PCG) 

14.9 

14.4 

14.9 

14.7 

12.1 

15. 

3 12. 

0 12.1 

(PCB) 

12.3 

16.4 

11.  7 

13.5 

10.3 

14. 

0 12. 

4 10.1 

(Fox) 

9.4 

12.  7 

11.4 

11.5 

7.6 

10. 

3 10. 

7 10.0 

-20- 


Table  18.  Comparative  growth  at  20°  C. 


Roots  Shoots 


20% 

40% 

60% 

Av. 

20% 

40% 

60% 

Av. 

(PCG) 

12.5 

10.  3 

8.5 

10.4 

9.0 

10.  3 

10.7 

10.0 

(PCB) 

11.9 

13.  7 

9.7 

11.8 

9.5 

11.6 

8.9 

10.0 

(Fox) 

11.9 

10.7 

8.5 

10.4 

9.3 

9.5 

9.0 

9.2 

Table  19. 

Comparative 

growth  at 

15°  C. 

Roots 

30% 

Shoots 

20% 

40% 

60% 

Av. 

40% 

60% 

Av. 

(PCG) 

10.4 

15.0 

12.0 

12.5 

9.9 

12.3 

14.  3 

12.2 

(PCB) 

12.1 

11.3 

12.3 

11.9 

10.  3 

10.  3 

10.3 

10.  3 

(Fox) 

10.6 

10.7 

10.5 

10.6 

8.4 

8.0 

8.6 

8.4 

Table  30. 

Comparative 

growth  at  10°  C. 

Roots 

20% 

Shoots 

60% 

20% 

40% 

60% 

Av. 

40% 

Av. 

(PCG) 

4.6 

3.0 

2.8 

3.5 

3.6 

1.8 

2.3 

2.2 

(PCB) 

2.  7 

2.2 

3.6 

3.6 

1.9 

1.9 

1.3 

1.7 

(Fox) 

1.2 

2.5 

1.7 

1.8 

1.0 

1.3 

2.0 

1.4 

For  ready  comparison,  ratios  derived  from  the  above 
data  are  shown  in  Table  21. 


Table  21.  Ratios  for  roots  and  shoots  at  different 
temperatures. 


Temperature 

(PCG) 

(PCB) 

(Fox) 

# 

o 

o 

o 

to 

Roots 

1.00 

1.00  : 

.97 

Shoots 

1.00 

.90  : 

.91 

25°  C. 

Roots 

1.00 

.92  : 

.78 

Shoots 

1.00 

.85  : 

.71 

-31- 


Table  31  (cont.). 


Temperature 

(PCG) 

(PCB) 

(Fox) 

30°  C. 

Roots 

1.00 

1.13 

1.00 

Shoots 

1.00 

1.00 

.93 

15°  C. 

Roots 

1.00 

.95 

.85 

Shoots 

1.00 

.84 

.69 

10°  C. 

Roots 

1.00 

.74 

.51 

Shoots 

1.00 

.77 

.64 

Mean  ratios 

- Roots 

1.00 

.95 

.83 

Shoots 

1.00 

.87 

.77 

(PCG ) germinated  more  rapidly  than  the  other  two 
types,  at  all  temperatures  used.  The  minimum  time  required 
was  3.3  days  for  (PCG)  at  30°  C. , and  the  maximum  was  35.7  days 
for  (Fox)  at  10°  C.  The  mean  ratios,  based  on  the  performance 
of  (PCG),  are  1.00:  1.07  : 1.12.  A slight  increase  in  the 
rapidity  of  germination  in  each  case  may  be  noted  as  the  soil 
moisture  is  increased  from  30$  to  60$  of  saturation. 

The  discrepancies  in  rates  of  germination  are  reflected 
in  the  results  of  the  measurements  of  seedling  growth.  (PCG) 
made  quite  consistently  a greater  growth  of  both  roots  and 
shoots  in  a given  period  of  time  than  the  other  two  strains  of 
corn.  Considering  both  root  and  shoot  growth,  the  mean  ratios 
for  the  three  strains  of  corn  were  1.00  : .91  : .79.  Of  the 
temperatures  used,  30°  gave  the  most  rapid  germination,  while 
35°  C.  seemed  somewhat  more  favorable  for  subsequent  growth. 

These  general  results  are  corroborated  by  the  exact  studies  of 
Lehenbauer  (14).  The  latter  found  that  for  periods  longer  than 
three  hours,  the  optimum  temperature  for  growth  of  com  is 





-23- 


between  29°  C.  and  32°  C. 


Vitality  as  influenced  by  soaking  in  water. 

The  relative  percentages  of  germination  of  seeds 
not  soaked,  and  of  seeds  soaked  in  water  at  several  temperatures 
for  different  periods  of  time,  were  determined.  Some  of  the 
teste  were  made  on  the  rag  doll  germinator,  and  others  in  soil 
cn  the  greenhouse  bench. 

25  seeds  of  each  strain  of  corn  were  soaked  in  water 
at  65°  C.  for  10,  20,  and  30  minutes  respectively.  75  seeds  of 
each  kind  were  used  as  unsoaked  checks.  Germinations  were  made 
at  30°  C.  on  the  modified  rag  doll  (8).  As  used  in  this  labor- 
atory a wire  core  insures  quite  uniform  aeration  in  all  parts 
of  the  doll.  The  results  are  shown  in  Table  22. 


Table  22.  Relative  vitality  after  soaking  in 

water  at  65°  C.  Ger^i^ated  ai  3o°C-. 

Time  Per  cent  germination 


Strong 

Weak 

Total 

(PCG) 

Not  soaked 

78 

22 

100 

(PCB) 

w 

n 

55 

45 

100 

(Pox  ) 

11 

n 

34 

62 

96 

(PCG) 

10 

min. 

76 

16 

92 

(PCB) 

10 

min. 

64 

36 

100 

(Fox) 

10 

min. 

52 

36 

88 

(PCG) 

20 

min. 

8 

52 

60 

(PCB) 

20 

min. 

0 

68 

68 

(Fox) 

20 

min. 

0 

32 

32 

(PCG) 

(PCB) 

30 

30 

min. 

min. 

0 

0 

12 

8 

12 

8 

(Fox) 

30 

min. 

0 

4 

4 

. 


-23- 

The  unsoaked  corn  gave  total  germination  ratios  of 
1.00  : 1.00  : .96,  for  (PCG),  (PCB)  and  (Fox)  respectively. 

The  percentages  themselves  coincide  with  the  data  furnished  by 
Mr.  Holbert (Table  l).  After  this  severe  treatment,  the  total 
percentages  of  germination  were  reduced  46$,  45$,  and  59$ 
respectively,  the  ratios  remaining  1.00  : 1.01  : .76.  Consider- 
ing the  quality  of  the  seedlings,  (PCG)  made  a somewhat  better 
showing  than  (PCB).  The  inferiority  of  (Fox)  becomes  more 
marked  as  the  conditions  affecting  growth  become  more  severe. 

In  a second  experiment,  seeds  of  each  strain  of  corn 
were  selected,  (a)  with  coats  intact,  (b)  with  coats  broken. 

10  kernels  of  each  were  soaked  in  water  at  60°  C.  for  10,  20, 
and  30  minutes,  and  at  65°  C.  for  5 and  10  minutes.  They  were 
then  planted  in  soil  at  1 inch  intervals,  on  the  greenhouse 
bench.  The  resulting  plants  are  shown  in  the  plat  at  the  right 
of  the  bench  (Plate  5).  The  average  results  of  the  treatment 
are  given  in  Table  23. 


Table  23. 

Results 

of 

soaking 

corn 

at  60° 

C.  and 

(PCG) 

(PCB) 

(Fox) 

(a) 

(b) 

(a) 

(b) 

(a) 

(b) 

Germination 

Checks 

100 

89 

100 

76 

100 

100 

Soaked 

64 

48 

68 

40 

76 

56 

Av.  heights 

(in. ) 

Checks 

16.2 

9.1 

15.4 

2.7 

14.7 

6.7 

Soaked 

14.9 

6.  3 

12.4 

4.4 

13.2 

5.  7 

. 


■ ) 


-24- 


Table  23  (cent.). 

(PCG)  (PCB)  (Fox) 


Av.  green 

(a) 

(b) 

(a) 

(b) 

(a) 

(b) 

weights (gms. 
Checks 

) 

2.59 

1.01 

2.13 

.28 

2.08 

1.02 

Soaked 

2.24 

.58 

1.69 

.32 

1.77 

.52 

Av.  dry 
weights (gms. 
Checks 

) 

.23 

.09 

.19 

.03 

.18 

.10 

Soaked 

.17 

.05 

.14 

.02 

.14 

.04 

Total  yields (gms.) 
Checks  2. 30 

.80 

1.90 

.23 

1.80 

1.00 

Soaked 

1.08 

.25 

1.02 

.19 

.95 

.23 

By  an  inspection  of 

Table 

23  it 

may 

be  seen 

that 

soaking  at  relatively  high  temperatures  affected  adversely, 
not  only  germination,  but  also  subsequent  growth  in  each  case. 

In  general  (PCG)  showed  more  resistance  than  (PCB).  (Fox)  was 
least  resistant.  Kernels  with  coats  intact  gave  uniformily 
better  results  than  kernels  with  coats  broken.  The  yield  from 
kernels  with  broken  coats  averaged  69$  less  than  that  from 
kernels  with  coats  intact,  without  soaking.  When  the  soaking 
treatment  was  applied,  the  reduction  averaged  78$. 

In  a more  extensive  experiment  the  soaking  was 
carried  on  at  temperatures  of  10°  C.  and  35°  C.,  for  varying 
periods  of  time.  The  seeds  used  were  (a)  with  coats  intact, 

(b)  with  coats  broken,  (c)  unselected.  After  treatment  10  seeds 
of  each  strain  of  corn  were  planted  in  soil  on  the  greenhouse 
bench.  The  plants  were  harvested  at  the  end  of  three  weeks. 

The  results  are  presented  in  Tables  24  to  28. 


-25- 


Table  24.  Germination;  kernels  intact  (a),  kernels 
broken  (b),  kernels  unselected  (c). 


Treatment 

(a) 

(PCG) 

(b) 

(c) 

(a) 

(PCB) 

(b) 

(c) 

(a) 

(Fox) 

(b) 

(c) 

10° 

C.-  1 

hr.  100 

100 

100 

90 

100 

100 

100 

100 

80 

10° 

C.  - 6 

hrs. 100 

90 

100 

100 

90 

90 

100 

” 70 

70 

10° 

C.  -12 

hrs. 100 

100 

80 

90 

100 

70 

90 

80 

60 

10° 

C.  -24 

hrs.  90 

100 

100 

100 

100 

100 

90 

70 

60 

10° 

C.  -48 

hrs.  90 

90 

100 

90 

90 

100 

80 

100 

60 

35® 

C.-  1 

hr.  100 

100 

90 

100 

100 

100 

90 

90 

90 

35® 

C.  - 6 

hrs. 100 

100 

100 

100 

100 

100 

100 

100 

90 

35® 

C.  -12 

hrs. 100 

100 

100 

100 

100 

100 

100 

100 

100 

35® 

C.-24 

hrs. 100 

80 

100 

100 

100 

100 

100 

100 

100 

35® 

C.-48 

hrs.  90 

100 

70 

100 

70 

80 

80 

50 

40 

Checks 

100 

89 

95 

100 

76 

100 

100 

100 

100 

Table  25, 

. Average 

heights  (in.) 

kernels  intact 

kernel 

s broken 

(b), 

kernels  unselec 

Treatment 

(a) 

(PCG) 

(PCB) 

(Fox) 

(b) 

(c) 

(a) 

(b) 

(c) 

(a) 

(b) 

(c) 

10® 

C.-  1 

hr.  16.4 

14.6 

16.5 

15.2 

13.2 

17. 

5 

16.9 

12.6 

15.7 

10° 

C.-  6 

hrs. 16. 2 

13.0 

17.4 

14.7 

10.5 

16. 

7 

17.6 

15.7 

15.5 

10® 

C.  -12 

hrs. 15. 8 

11.5 

16.3 

16.8 

8.7 

15. 

6 

18.1 

13.5 

14.2 

10® 

C.  -24 

hrs. 16. 9 

15.6 

19.3 

18.3 

14.5 

17. 

1 

16.2 

15.3 

15.0 

10-s 

C.  -48 

hrs. 16. 9 

16.9 

15.3 

18.7 

13.6 

16. 

8 

17.7 

15.5 

14.3 

35® 

C.-  1 

hr.  16.2 

13.2 

16.2 

15.5 

7.2 

16. 

2 

15.5 

14.1 

14.9 

35® 

C.-6  hrs.  18.0 

15.8 

17.0 

16.3 

9.1 

16. 

0 

17.4 

15.8 

16.5 

35° 

C. -12 

hrs. 15. 7 

16.1 

16.1 

14.  5 

12.3 

14. 

0 

17.8 

15.9 

15.9 

35° 

C .-24 

hrs. 18. 5 

12.3 

19.5 

17.4 

10.7 

16. 

3 

10.5 

10.9 

15.9 

35® 

C.  —48 

hrs. 16.4 

13.7 

15.5 

14.9 

12.0 

15. 

5 

17.3 

13.5 

14.9 

Checks 

16.2 

9.1 

18.3 

15.4 

2.7 

16. 

1 

14.7 

6.  7 

16.4 

-26- 


Table  26.  Average  green  weights  (grams);  kernels 

intact  (a),  kernels  broken  (b),  kernels 
unselected  (c). 

Treatment  (PCG)  (PCB)  (Fox) 


(a) 

(b) 

(c) 

(a) 

(b) 

(c) 

(a) 

(b) 

(c) 

10° 

C.-  1 

hr.  2.02 

1.49 

2.67 

1.69 

1.67 

2.76 

2.44 

1.38 

2.68 

10° 

C.-  6 

hre. 1. 62 

1.06 

2.51 

1.47 

.94 

2.66 

2.27 

1.91 

2.24 

10° 

C.  -12 

hrs. 2. 27 

1.12 

2.27 

2.18 

.79 

1.96 

2.75 

1.60 

2.16 

10° 

C.  -24 

hrs. 2. 29 

1.59 

1.36 

2.23 

1.84 

2.  65 

1.85 

1.85 

2.14 

10° 

C.  -48 

hre. 2.06 

2.23 

2.25 

2.29 

1.57 

2.62 

2.73 

1.92 

1.80 

35° 

C.-  1 

hr.  1.94 

1.32 

3.05 

1.79 

.75 

2.47 

1.78 

1.85 

2.49 

35° 

C.  - 6 

hrs. 2. 73 

1.65 

3.16 

1.80 

1.00 

2.31 

2.28 

1.95 

2.61 

35° 

C.  -12 

hrs. 2.94 

2.06 

2.44 

1.56 

1.56 

1.56 

2.85 

2.09 

2.46 

35° 

C.  -24 

hrs. 2. 49 

1.21 

3.  60 

2.15 

1.05 

2.42 

2.24 

1.25 

2.62 

35° 

C.  -48 

hrs. 2. 25 

1.73 

2.74 

1.67 

1.33 

2.  38 

2.78 

1.28 

2.34 

Checks 

2.59 

1.01 

2.93 

2.13 

.28 

2.24 

2.08 

1.02 

2.62 

Table  27.  Average  dry  weights  (grams);  kernels 

intact  (a),  kernels  broken  (b),  kernels 
unselected  (c). 


Treatment 

(PCG) 

(PCB) 

(Fox) 

(a) 

(b) 

(c) 

(a) 

(b) 

(c) 

$a) 

(b) 

(c) 

10°  C.-  1 

hr. 

.18 

.14 

.18 

.14 

.14 

. 20 

.21 

.12 

.17 

10°  C.-  6 

hrs. 

.18 

.08 

.17 

.13 

.07 

.18 

.20 

.17 

.15 

10°  C. -12 

hrs. 

.18 

.09 

.15 

.18 

.06 

.13 

.24 

.13 

.14 

10°  C. -34 

hrs. 

. 21 

.15 

.13 

.21 

.16 

.18 

.17 

.17 

.14 

10°  C .-48 

hrs. 

.18 

.22 

.16 

.20 

.15 

.18 

.17 

.19 

.14 

35°  C.-  1 

hr. 

.16 

.13 

.21 

.12 

.06 

.19 

.12 

.15 

.18 

35°  C.-  6 

hrs. 

.26 

,17 

.12 

.17 

.09 

.17 

.20 

.18 

.19 

35°  C.-12 

hrs. 

.18 

.20 

.18 

.14 

.13 

.12 

.26 

.20 

.18 

35°  C. -24 

hrs. 

.23 

.12 

.16 

.20 

.09 

• IE 

.20 

.11 

.19 

35°  C.-48 

hrs. 

.22 

.17 

.19 

.15 

.11 

.16 

.25 

.12 

.14 

Checks 

.23 

.09 

.21 

,19 

.03 

,16 

.18 

.10 

.19 

-27- 


Table  28.  Total  yields  (grams);  kernels  intact  (a), 

kernels  broken  (b),  kernels  unselected  (e) . 


Treatment 

(a) 

(PCG) 

(b) 

(c) 

(a) 

(PCB) 

(b) 

(c)  (a) 

(Fox) 

(b) 

(c) 

10° 

C.-  1 

hr.  1.79 

1.43 

1.82 

1.30 

1.41 

1.98  2.07 

1.17 

1.35 

10* 

C.-  6 

hrs. 1. 79 

.74 

1.72 

1.28 

.60 

1.61  2.00 

1.06 

1.09 

10° 

C.  -12 

hrs. 1 . 83 

.94 

1.24 

1.67 

.53 

.89  1.89 

1.07 

.86 

10° 

C.  -24 

hrs. 1.90 

1.52 

1.32 

2.14 

1.25 

1.79  1.55 

1.23 

.84 

10° 

C • —48 

hrs. 1. 62 

1.96 

1.60 

1.81 

1.49 

1.84  1.40 

1.86 

.82 

35° 

C.-  1 

hr.  1.56 

1.29 

1.88 

1.23 

.58 

1.91^1.11 

1.38 

1.64 

35° 

C.-  6 

hrs . 2.  59 

1.67 

1.22 

1.74 

.90 

1.72*1.97 

1.83 

1.69 

35° 

C.  -12 

hrs. 1. 83 

2.02 

1.77 

1.43 

1.22 

1.16  2.64 

2.02 

1.81 

35° 

C.  -24 

hrs. 2.  34 

.93 

1. 75 

1.97 

.95 

1.84*  2.03 

1.15 

1.88 

35° 

C.-48 

hrs. 1. 96 

1.66 

1.33 

1.35 

.75 

1.31  2.05 

.58 

.55 

Checks 

2.30 

.80 

2.14 

1.90 

.23 

1.65  1.80 

1.00 

1.90 

Table  29.  Summary  of  data  in  Tables  24  to  28. 
(PCG)  (PCB)  (Fox) 


(a) 

Germination ($) 

(b) 

(c)  (a) 

(b) 

(c) 

(a) 

(b) 

(c) 

Checks  100 

89 

95 

100 

76 

100 

100 

100 

100 

Soaked  97 

96 

94 

97 

95 

94 

93 

86 

75 

Av.  Heights(in.) 


Checks 

16.2  9.1 

18.  3 

15.4 

2.7  16.1  14.7  6.7  16.4 

Soaked 

16.7  14.3 

16.9 

16.1 

11.2  16.3  17.0  14.3  15.3 

Av.  green 

weights  (grams 

i) 

Checks 

2.59  1.01 

2.93 

2.13 

.28  2.24  2.08  1.02  2.62 

Soaked 

2.26  1.55 

2.60 

1.88 

1.242.38  2.40  1.71  2.35 
) 1 

Av.  dry  weights  (grams) 

Checks 

.23  .09 

.21 

.19 

.03  .16  .18  .10  .19 

Soaked 

.20  .15 

.16 

.16 

.11  .17  .20  .15  .16 

Total  yields  (grams) 

Checks 

2.30  .80 

2.14 

1.90 

.23  1.65  1.80  1.00  1.90 

Soaked 

1.92  1.42 

1.56 

1.59 

.97  1.60  1.87  1.33  1.25 

The  outstanding  fact  to  be  noted  from  Table  29  is 
the  reduction  in  yields  when  kernels  with  broken  coats  are  used 
in  contrast  to  kernels  with  coats  intact.  This  holds  true 


I ' I 


<• 


-28- 


quite  consistently  for  germination,  average  heights,  average 

green  and  dry  weights,  and  the  expression  of  all  of  these  in 

were 

the  total  yields.  There  apparently  no  significant  differ- 
ences in  this  respect  between  the  three  strains  of  corn.  Con- 
sidering all  the  plantings,  the  use  of  kernels  with  seed  coats 
broken  resulted  in  a reduction  of  44$  in  the  average  dry  weight 
of  the  plants,  and  a reduction  of  48$  in  the  total  yield. 

Brown  (3),  comparing  the  field  performances  of  entire  and  broken 
seeds  obtained  an  average  reduction  in  yield  with  broken  kernels 
of  11$.  In  other  experiments  (2)  with  dehulled  seeds,  a reduc- 
tion in  yield  of  12$  was  noted. 

Considering  all  the  plantings,  the  total  yields  of 
(PCB)  averaged  26$,  and  of  (Fox),  9$,  below  those  of  (PCG).  The 
data  obtained  with  composite  samples  would  in  general  indicate 
some  decreases  in  yield  due  to  soaking  at  medium  temperatures. 
The  apparent  exception  in  the  case  of  the  plantings  with  broken 
kernels,  is  quite  possibly  explained  by  the  position  of  the 
ohecks  adjacent  to  a row  of  kernels  intact  which  had  been  soaked 
for  48  hours.  The  latter  germinated  somewhat  more  rapidly, 
and  possibly  exerted  an  undue  influence  through  competition, 
in  view  of  the  close  planting  in  the  plat.  (See  Plate  5,  first 
row  in  second  plat  from  the  left). 

Kidd  and  West  (12)  on  the  basis  of  their  own  work 
and  that  of  previous  investigators,  draw  the  conclusion  that 
presoaking,  particularly  in  an  excess  of  water,  is  generally 
harmful.  Considering  all  the  plantings,  and  having  in  mind 


-39- 


the  total  yields,  it  appears  that  the  soaking  at  10°  C.  may 
be  somewhat  more  injurious  than  soaking  at  35°  C.  No  signifi- 
cant differences  were  observed  between  the  three  strains  of 
corn  in  this  respect. 

Vitality  as  influenced  by  the  growth  of  fungi 

Study  was  made  of  the  effects  of  superficial  fungi 
on  germination  in  the  three  strains  of  corn.  The  fungi  used 
were  ieolated  from  corn  on  the  germinator,  and  included  strains 
of  Fusarium  moniliforme,  Penicillium,  Rhizopus,  and  Aspergillus. 
Fusarium  moniliforme  is  recognized  as  a very  active  parasite 
on  corn.  ■Pwai-giilim  Aspergillus  may  cause  considerable 
losses  in  the  field  (18).  Rhizopus  is  commonly  present,  and 
has  been  noted  as  a weak  parasite  on  the  germinator  (l). 

This  investigation  however,  did  not  involve  primarily 
any  comparisons  of  relative  pathogenicity  of  the  fungi  employed. 
They  were  used  as  a means  of  measuring  the  relative  resistance 
of  the  three  kinds  of  corn  under  test.  Untreated  seeds,  as 
well  as  others  which  had  been  subjected  to  presoaking  treatments 
designed  to  reduce  their  vitality,  were  used.  In  order  to  in- 
eure  a uniform  distribution  of  the  spores,  the  seeds  were  soaked 
for  15  minutes  in  a spore  suspension.  They  were  then  placed 
on  blotters  above  plaster  of  paris  blocks  in  germinator  pans, 
under  favorable  temperature  conditions.  As  the  interiors  of 
the  germinators  were  scalded  before  use,  the  various  fungi  grew 


. 

. 

. 


- 


■ 


. 

. 


. -<»«r 


-30- 


in  fairly  pure  cultures.  A series  of  checks  and  a series  of 
kernels  covered  with  spores  were  placed  in  each  pan,  20  to  25 
seeds  being  used  in  each  case.  Typical  cultures  are  shown  in 
Plates  6 to  12.  The  average  results  for  a number  of  experiments 
are  shown  in  Table  30. 


Table  30.  Vitality  as  affected  by  fungi 

Treatment  Per  cent  germination 

(PCG)  (PCBj  (Fox) 


Str. 

Wk. 

Tot. 

Str 

. Wk. 

Tot. 

Str. 

Wk. 

Tot 

Not  soaked 

No  spores 

81 

18 

99 

68 

32 

100 

57 

38 

95 

Fusarium 

78 

15 

94 

71 

13 

84 

33 

6 

39 

Penicillium 

74 

23 

97 

70 

29 

99 

40 

44 

84 

Rhizopus 

56 

44 

100 

58 

38 

96 

34 

60 

94 

Aspergillus 
Soaked  at  10° 

76 

C., 

23 

99 

79 

21 

100 

49 

48 

97 

24  hrs. 

No  spores 

93 

5 

98 

71 

21 

96 

53 

30 

83 

Fusarium 

75 

35 

100 

35 

65 

100 

5 

60 

65 

Penicillium 

85 

10 

95 

75 

30 

95 

50 

40 

90 

Aspergillus 
Soaked  at  10° 

60 

c.5 

40 

100 

70 

25 

95 

30 

50 

80 

48  hrs. 

No  spores 

90 

10 

100 

65 

30 

95 

50 

32 

82 

Fusarium 

30 

70 

90 

55 

45 

100 

0 

30 

30 

Aspergillus 

100 

0 

100 

55 

35 

80 

35 

35 

60 

In  another  series,  kernels  with  coats  intact,  and 
kernels  with  coats  broken,  were  used.  The  results  may  be  seen 
in  Table  31. 


-31 


Table  31.  Comparative  vitality  of  kernels  with 
coats  intact  and  coats  broken. 

Treatment  Per  cent  germination 

Str.  Wk.  Tot.  Str.  Wk.  Tot.  Str.  Wk.  Tot. 


Kernels  intact 

No  spores 

100 

0 

100 

95 

5 

100 

55 

30 

85 

Fusarium 

90 

10 

100 

90 

5 

95 

45 

35 

70 

Kernels  broken 

No  spores 

90 

10 

100 

90 

5 

95 

45 

35 

70 

Fusarium 

55 

30 

75 

60 

35 

85 

55 

10 

65 

\ 


In  the  above  experiments,  it  may  be  noted  in  general 
that  the  germinating  spores  of  Fusarium,  Penicillium,  Rhizopus, 
and  Aspergillus  were  effective  in  reducing  the  germination  of 
the  corn  in  the  order  named.  The  effect  of  the  fungous  mycelium 
was  most  marked  on  (Fox)  in  every  case,  and  in  general,  the 
least  impression  was  made  on  (PCG).  There  may  be  seen  in  general 
a direct  correlation  between  the  severity  of  soaking  and  injury 
attributable  to  the  fungi. 

Fusarium  produced  the  more  severe  effects  on  the 
kernels  with  broken  coats.  Miss  Hurd  (10)  has  shown  a direct 
relation  between  seed-coat  injury  and  susceptibility  to  molds 
and  fungicides,  in  the  casefof  wheat  and  barley. 


- 


' 

■ 


••  . 


. 


. 


■ 


-32- 


IV.  Discussion 

The  corn  used  in  the  present  investigation  showed  but 
slight  differences  in  vitality  in  ordinary  germinator  tests. 

But  when  adverse  conditions  are  encountered,  more  marked  differ- 
ences are  to  be  seen.  Strain  (PCG)  is  most  resistant,  and  (Fox) 
the  most  susceptible  to  injury. 

The  constant  differences  in  the  rates  of  water  absorp- 

are 

tion  improbably  to  be  explained  on  the  basis  of  physical  compo- 
sition of  the  kernels.  The  percentages  of  starchy  kernels  in 
the  three  types  of  corn  may  be  correlated  directly  with  the 
relative  rates  of  water  intake.  Leaching  was  also  apparently 
somewhat  greater  in  the  cases  of  the  (PCB)  and  (Fox)  strains, 
although  attempts  to  measure  these  differences  with  the  refract- 
oroeter  were  not  successful.  Kidd  and  West  (12)  would  attribute 
injury  by  soaking  to  the  leaching  of  soluble  food  reserves  to- 
gether with  an  accumulation  of  carbon  dioxide  in  the  seed. 

Results  obtained  in  the  present  work,  and  those  of 
Brown  (2,3)  clearly  indicate  that  broken  kernels  exhibit  a 
relatively  lower  vitality  than  entire  kernels.  Cracked  or 
abraded  kernels  due  to  injury  in  handling,  shelling,  or  planting 
by  machinery  are  common.  This  is  doubtless  true  to  a greater 
extent  with  the  rougher  types  of  corn.  For  example,  the  percent- 
ages of  broken  kernels  to  be  found  in  composite  samples  of  the 


. 


- 

. 


-33- 


corn  used  in  this  investigation  are  as  follows:  (PCG)  8.8$, 

(PCB)  21.0$,  (Fox)  36.5$;  this  in  spite  of  the  fact  that 
thi^  corn  had  not  been  handled  by  machinery,  and  the  rougher 
ears  had  been  wrapped  in  paper  to  prevent  damage.  Under  ordinary 
conditions  the  discrepancies  in  percentages  of  broken  kernels 
would  probably  be  even  greater. 

In  view  of  the  facts  presented  thus  far  it  seems 
probable  that  broken  kernels  play  a considerable  part  in  deter- 
mining the  results  obtained  with  apparently  disease-free  com 
in  field  experiments.  Holbert  (9)  for  example,  obtained  with 
(PCG)  and  (PCB),  both  practically  disease-free,  differences  in 
yield  of  20  bushels  or  more  per  acre,  in  infested  soil.  The 
differences  obtained  on  clean  soil  were  less  marked.  Again, 
four  years’  trial  at  Nebraska  with  smooth  and  rough  selections 
within  the  variety  resulted  in  an  average  decrease  in  yield  of 
3.5  bushels  per  acre,  or  7$,  when  rough  corn  was  used. 

Reductions  in  yield  of  12$  to  40$,  due  to  broken 
kernels,  indicate  that  Holbert’s  results  in  the  field  may  be 
due  at  least  in  part,  to  a similar  cause.  The  greater  differ- 
ences obtained  on  infested  soil  are  of  interest  in  connection 
with  the  demonstrated  effects  of  fungi  on  broken  kernels.  It 
has  been  shown  in  the  present  investigation,  and  likewise  by 
M iss  Hurd(lO),  that  kernels  with  broken  coats  are  more  suscep- 
tible to  injury  by  fungi  present  superficially,  than  are  kernels 


. . 


. 

. 

. 

-34- 


with  coats  intact.  The  work  of  Richey  (15)  indicates  that 
spores  carried  externally  on  the  seed  may  ordinarily  be  a 
factor  of  considerable  importance  in  the  field.  This  chain 
of  evidence  is  to  say  the  least,  most  suggestive. 

V.  Conclusions 

1.  The  rate  of  water  absorption  is  greatest  in  the 
types  of  corn  containing  the  higher  percentages  of  starchy 
kernels.  The  rate  is  least  with  (PC G) , a comparatively  horny 
type  of  corn. 

2.  The  temperature  coefficient  of  absorption  is 
about  1.4  in  all  three  strains. 

3.  Strain  (PCG)  exhibits  slight  though  constantly 
higher  rates  of  germination  and  growth  at  various  temperatures 
in  comparison  with  the  other  two  strains. 

4.  Entire  kernels  show  greater  vitality  than  broken 
kernels,  under  all  conditions. 

5.  Soaking  is  in  general,  apparently  injurious  to 
the  subsequent  growth  of  corn. 

6.  Superficial  fungi  are  detrimental  to  germination, 
especially  in  the  case  of  (Fox)  corn.  This  effect  is  heightened 
by  presoaking  treatments. 

7.  The  higher  percentages  of  broken  kernels  obtaining 
in  the  rougher  types  of  corn  is  offered  as  the  most  probable  ex- 
planation for  the  poor  showing  often  made  by  such  types  in  the 
field. 


. 


-35- 


VI.  Acknowledgment 

The  author  wishes  to  express  his  appre- 
ciation of  the  assistance  extended  by  Dr.  C.  F. 

Hottes,  Professor  of  Plant  Physiology  in  the  Uni- 
versity of  Illinois,  under  whose  direction  the 
work  was  carried  out.  By  inspiration  and  advice 
he  has  contributed  largely  to  the  success  attained. 

Thanks  are  also  due  him  for  the  use  of 
the  constant  temperature  cases  in  the  Plant  Physiology 
Laboratories. 


. - - 

- 

' 

t it 


-36- 


VII.  Literature  cited 


(1)  Adams,  J.  F.  & Russel,  A.  M.  Rhizopus  infection  of  corn 

on  the  germinator.  Phytopath.  10:535-543.  1920. 

(2)  Brown,  E.  B.  Effects  of  mutilating  the  seeds  on  the  growth 

and  productiveness  of  corn,  U.  S.  Dept.  Agri  Bull.  1011. 
1922. 

(3)  Brown,  E.  B.  Relative  yields  of  broken  and  entire  kernels 

of  seed  corn.  Jour.  Am.  Soc.  Agron.  12:196-197.  1920. 

(4)  Brown,  A.  J.  & Worley,  F.  P.  The  influence  of  temperature 

on  the  absorption  of  water  by  seeds  of  Hordeum  vulgare 
in  relation  to  the  temperature  coefficient  of  chemical 
change.  Proc.  Roy.  Soc.  Lond.  B85:546-553.  1912. 

(5)  Burrill,  T.  J.  & Barrett,  J.  T.  Dry  rot  of  corn.  111.  Circ, 

117.  1908. 

(6)  Burrill,  T.  J.  & Barrett,  J.  T.  Ear  rots  of  corn.  111. 

Exp.  Sta.  Bull.  133.  1909. 

(7)  Denny,  F.  E.  Permeability  of  certain  plant  membranes  to 

water.  Bot.  Gaz.  63:373-397.  1917. 

(8)  Duddleston,  B.  H.  The  modified  rag  doll  and  germinator 

box.  Purdue  Exp.  Sta.  Bull.  236.  1920. 

(9)  Holbert,  J.  R.  Address,  Corn  Growers  and  Stockmens' 

Convention,  Urbana,  111.  Jan.,  1922. 

(10)  Hurd,  Annie  M.  Seed-coat  injury  and  viability  of  seeds  of 

wheat  and  barley  as  factors  in  susceptibility  to  molds 
and  fungicides.  Jour.  Agr.  Res.  21:99-122.  1921. 

(11 ) Kanitz,  A.  Temperatur  and  Lebensvorgange.  1915. 

(12)  Kidd,  F.  & West,  C.  Physiological  pre-determination:  the 

influence  of  the  physiological  condition  of  the  seed 
upon  the  course  of  subsequent  growth  and  upon  the  yield. 
I.  The  effects  of  soaking  seeds  in  water.  IV.  Review 
of  literature.  Ann.  Appl.  Biol.  5:1-10,  220-251.  1918  - 
1919. 


-37- 


(13)  Kiesselbach,  T.  A.  & Ratcliff,  J.  A.  Freezing  injury  of 

seed  corn.  Nebr.  Exp.  Sta.  Res.  Bull.  16.  1920. 

(14)  Lehenbauer,  P.  A.  Growth  of  maize  seedlings  in  relation 

to  temperature.  Physiological  Researches  1:247-288.  1914. 

(15)  Richey,  F.  D.  Formaldehyde  treatment  of  seed  corn. 

Jour.  Am.  Soc.  Agron.  12:39-43.  1920. 

(16)  Shull,  C.  A.  Address,  A.  A.  A.  S.,  Chicago.  Dec.,  1920. 

(17)  Shull,  C.  A.  Temperature  and  rate  of  moisture  intake  in 

seeds.  Bot.  Gaz.  69:361-390.  1920. 

(18)  Taubenhaus,  J.  J.  A study  of  the  black  and  yellow  molds 

of  ear  corn.  Texas  Exp.  Sta.  Bull.  270.  1920. 


-38- 

VIII.  Plates 
Explanation  of  plates. 


Plate 

I. 

Ears 

of 

"Peoria  Co. 

Good" (PCG). 

Plate 

II. 

Ears 

of 

"Peoria  Co. 

Bad" (PCB). 

Plate 

III. 

Ears 

of 

"Fox" (Fox) . 

Plate 

IV. 

Ears 

of 

(PCG),  (PCB) 

, (Fox ) . 

Plate 

V. 

Results 

of  soaking  corn.  Left 

Plate  VI . 
Plate  VII. 
Plate  VIII 
Plate  IX. 
Plate  X. 
Plate  XI. 


Plat  1.  Kernels  intact,  10°  C.  and  35°  C. 

Plat  3.  Kernels  broken,  10°  C.  and  35°  C. 

Plat  3.  Kernels  intact  and  broken,  60°  C.  and  65°C 

Penicillium;  no  presoaking. 

Penicillium;  24  hrs.  at  10°  C. 

Penicillium;  48  hrs.  at  10°  G. 

Fusarium;  no  presoaking. 

Fusarium;  34  hrs.  at  10°  C. 

Fusarium;  48  hrs.  at  10°  C. 


From  left  to  right:  (PCG),  (PCB),  (Fox).  The  checks  are 
in  the  foreground  in  each  case. 


Plate  I 


Plate  III 


Plate  IV 


Plate  VI. 


~4&- 


Plate  VII. 


-46- 


Plate  VIII. 


-47- 


1 


Plate  IX. 


Plate  X. 


-49- 


Plate  Xt. 


-50- 


IX.  Vita 

Frederick  Franci3  Weinard  was  born  at  Lincoln, 
Nebraska,  December  2,  1893.  He  attended  the  public  and 
parochial  schools  of  the  City,  graduating  from  the  Lincoln 
High  School  in  the  year  1912.  In  the  autumn  of  1912  he 
entered  the  University  of  Nebraska,  which  he  attended  for 
the  ensuing  five  years.  He  received  the  B.  S.  degree  in 
1916,  and  was  elected  to  active  membership  in  Sigma  Xi  the 
same  year.  He  was  granted  the  M.  A.  degree  in  1917. 

The  months  of  June  to  December,  1917,  were  spent 
as  Field  Assistant  in  the  Office  of  Forest  Pathology,  U.  S. 
Department  of  Agriculture.  The  time  from  December,  1917, 
to  August,  1919,  was  spent  in  the  U.  S.  Army  (Medical  Depart- 
ment ) . 

Since  September,  1919,  the  author  of  this  thesis 
has  been  a graduate  student  and  Assistant  in  Botany  in  the 
University  of  Illinois.  In  1920  he  received  the  honor  of 
membership  in  the  Gamma  Alpha  Graduate  Scientific  Fraternity. 


